<meta charset="utf-8">
(#) Using 'px' dimension

!!! WARNING: Using 'px' dimension
   This is a warning.

Id
:   `PxUsage`
Summary
:   Using 'px' dimension
Severity
:   Warning
Category
:   Correctness
Platform
:   Android
Vendor
:   Android Open Source Project
Feedback
:   https://issuetracker.google.com/issues/new?component=192708
Since
:   Initial
Affects
:   Resource files
Editing
:   This check runs on the fly in the IDE editor
See
:   https://developer.android.com/guide/practices/screens_support.html#screen-independence
Implementation
:   [Source Code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-checks/src/main/java/com/android/tools/lint/checks/PxUsageDetector.java)
Tests
:   [Source Code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-tests/src/test/java/com/android/tools/lint/checks/PxUsageDetectorTest.java)
Copyright Year
:   2011

For performance reasons and to keep the code simpler, the Android system
uses pixels as the standard unit for expressing dimension or coordinate
values. That means that the dimensions of a view are always expressed in
the code using pixels, but always based on the current screen density.
For instance, if `myView.getWidth()` returns 10, the view is 10 pixels
wide on the current screen, but on a device with a higher density
screen, the value returned might be 15. If you use pixel values in your
application code to work with bitmaps that are not pre-scaled for the
current screen density, you might need to scale the pixel values that
you use in your code to match the un-scaled bitmap source.

!!! Tip
   This lint check has an associated quickfix available in the IDE.

(##) Example

Here is an example of lint warnings produced by this check:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~text
res/layout/now_playing_after.xml:41:Warning: Avoid using "px" as units;
use "dp" instead [PxUsage]
    android:layout_width="2px"
    --------------------------
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Here is the source file referenced above:

`res/layout/now_playing_after.xml`:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~xml linenumbers
&lt;?xml version="1.0" encoding="utf-8"?&gt;
&lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/now_playing"
    android:layout_width="fill_parent"
    android:layout_height="@dimen/now_playing_height"
    android:orientation="horizontal"&gt;
    &lt;LinearLayout
        android:background="@color/background2"
        android:paddingLeft="14dip"
        android:paddingRight="14dip"
        android:paddingTop="10dip"
        android:paddingBottom="10dip"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:layout_weight="1"
        android:orientation="vertical"&gt;
        &lt;TextView
            android:id="@+id/now_playing_title"
            android:duplicateParentState="true"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:textStyle="bold"
            android:textSize="@dimen/text_size_large"
            android:textColor="@color/foreground1"
            android:text="@string/now_playing_after_title"
            android:maxLines="2"
            android:ellipsize="end" /&gt;
        &lt;TextView
            android:id="@+id/now_playing_subtitle"
            android:duplicateParentState="true"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:paddingTop="3dip"
            android:textColor="@color/foreground2"
            android:textSize="@dimen/text_size_small"
            android:text="@string/now_playing_after_subtitle"
            android:singleLine="true"
            android:ellipsize="end" /&gt;
    &lt;/LinearLayout&gt;
    &lt;View
        android:layout_width="2px"
        android:layout_height="fill_parent"
        android:background="@android:color/white" /&gt;
    &lt;ImageButton
        android:background="@drawable/btn_now_playing_more"
        android:id="@+id/now_playing_more"
        android:src="@drawable/ic_now_playing_logo"
        android:padding="12dip"
        android:layout_width="100mm"
        android:layout_height="120in"
        android:onClick="onNowPlayingLogoClick"
        android:maxHeight="1px"
        android:scaleType="center" /&gt;
&lt;/LinearLayout&gt;
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

You can also visit the
[source code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-tests/src/test/java/com/android/tools/lint/checks/PxUsageDetectorTest.java)
for the unit tests for this check to see additional scenarios.

The above example was automatically extracted from the first unit test
found for this lint check, `PxUsageDetector.testPxWarnings`.
To report a problem with this extracted sample, visit
https://issuetracker.google.com/issues/new?component=192708.

(##) Suppressing

You can suppress false positives using one of the following mechanisms:

* Adding the suppression attribute `tools:ignore="PxUsage"` on the
  problematic XML element (or one of its enclosing elements). You may
  also need to add the following namespace declaration on the root
  element in the XML file if it's not already there:
  `xmlns:tools="http://schemas.android.com/tools"`.

  ```xml
  &lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;resources xmlns:tools="http://schemas.android.com/tools"&gt;
      ...
      &lt;style tools:ignore="PxUsage" .../&gt;
    ...
  &lt;/resources&gt;
  ```

* Using a special `lint.xml` file in the source tree which turns off
  the check in that folder and any sub folder. A simple file might look
  like this:
  ```xml
  &lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;lint&gt;
      &lt;issue id="PxUsage" severity="ignore" /&gt;
  &lt;/lint&gt;
  ```
  Instead of `ignore` you can also change the severity here, for
  example from `error` to `warning`. You can find additional
  documentation on how to filter issues by path, regular expression and
  so on
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/lintxml.md.html).

* In Gradle projects, using the DSL syntax to configure lint. For
  example, you can use something like
  ```gradle
  lintOptions {
      disable 'PxUsage'
  }
  ```
  In Android projects this should be nested inside an `android { }`
  block.

* For manual invocations of `lint`, using the `--ignore` flag:
  ```
  $ lint --ignore PxUsage ...`
  ```

* Last, but not least, using baselines, as discussed
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/baselines.md.html).

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